White Pozzolan Manufactured From Post-Consumer Waste Glass, Products Incorporating the Same and Methods of Manufacturing the Same

ABSTRACT

A clean dry white glass powder useful as a substitute for Portland cement in concrete, in paints, and for other known uses for glass powder produced conventionally can be produced from unsorted post-consumer waste glass, including a substantial fraction of non-glass items, by employing glass pulverizing equipment to reduce waste glass to small fragments, allowing removal of trash, employing a multistep washing process to clean the glass fragments, in the preferred embodiment using aggregate cleaning equipment, drying the fragments, preferably using fluidized bed techniques, and grinding the glass to a desired particle size, preferably using a ball mill, in combination with an air classification step to produce a bright white glass powder of uniform particle size.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to producing clean and dry glass powder fromunsorted post-consumer waste glass and its use in applicationsincluding, but not limited to, concrete mixes, paint additives, andfiller media.

2. State of the Art

Glass powder has been produced for years in limited quantities and isavailable to some extent for industrial applications. At present, glasspowder is created from fiberglass raw material rejects and industrialwaste from a fiberglass manufacturing operation, both of which areavailable in only selected locations. Increasing transportation costshave made it desirable to use glass that is available locally. Thisfact, and the glut of post-consumer waste glass available, makespost-consumer waste glass a logical choice for manufacture of glasspowder. However, post-consumer waste glass has drawbacks as a feedstock,in particular its tendency to be contaminated with various foodstuffsand chemical residues, and to be mixed with trash, including labels andother paper scraps, as well as ceramic, plastic, and metal items ofvarious sorts. These issues must be addressed and overcome in order toprocess post-consumer waste glass into usable glass powder in industrialquantities.

More specifically, for some years it has been commonplace for consumersto be expected to sort out empty glass containers for recycling.Ideally, this waste glass would be recycled as new containers. However,post-consumer waste glass is most often produced in various colors(clear, green, and brown being the most common) and cannot be sortedeconomically either manually or by automated equipment. Moreover,post-consumer waste glass tends to be mixed with plastic and ceramicwaste, as well as undifferentiated trash. The difficulty of separatingthe glass from these other materials and separating the glass into itsvarious colors has precluded efficient recycling of glass into newcontainers; as a result, most waste glass is now disposed of inlandfills, a highly inefficient and undesirable end for this valuablematerial.

At the same time, it is known that under proper circumstances glasspowder can serve as a substitute for some fraction of the Portlandcement commonly used in concrete. While large glass particles areundesired as a component in concrete, due to a well-knownalkali-silicate reaction (ASR) occurring between the alkalis of theglass and the silica of the aggregate components of the concrete, whichweakens the concrete, it is known that when the glass is powdered itbehaves as a pozzolanic material, that is, will exhibit a cementingproperty when mixed into a moistened mixture having a very high pH(e.g., 12.5). See, for example, Shayan, Value-Added Utilisation of WasteGlass in Concrete, IABSE Symposium Melbourne 2002; Use of Recycled Glassfor Concrete Masonry Blocks, Carver et al, NYSERDA Report 97-15 (1997).Portland cement is in short supply from time to time. Accordingly itwould be desirable if an efficient process for making high-quality,clean, dry powdered glass from post-consumer waste glass could beprovided. The powdered glass thus made could be used in partialsubstitution for Portland cement in concrete and in other applicationsnow known for powdered glass, e.g., paints and fillers for variousproducts and uses.

U.S. Pat. No. 6,296,699 to Jin for “Inorganic binders employing wasteglass” discusses using waste glass powder in concrete and “artificialstone”. An alkali metal activator, for example, an alkali metalhydroxide, silicate, aluminate, carbonate, sulfate, phosphate orfluoride is mixed with the glass powder and water, and this material iscured, in some examples at room temperature. Jin teaches that the wasteglass should be cleaned in advance to remove residues such as sugar fromthe waste glass which can affect the setting and binding of theconcrete. He further states that the processes used to create glasspowder from waste glass, e.g., ball milling and pulverizing, are wellknown.

In a report titled “Recycling of Crushed Glass into Coating Products”,CWC Report No. GL-96-1 (1998) the authors state that “paint and coatingapplications are especially sensitive to organic contamination. Forexample, one unwashed jar of mayonnaise could provide enough residue tobacterially contaminate many gallons of paint.”

Vitunac et al U.S. Pat. Nos. 5,350,121 and 5,246,174 show methods forrecycling glass, directed primarily to recycling of TV picture tubes,with much attention to removing heavy metals, coatings and the like.Pulverizing, washing, rinsing and further crushing steps are disclosedgenerally.

Abernathy U.S. Pat. No. 4,030,670 shows a trash recycling systemincluding separation of various sorts of trash. Glass fragments arewashed and dried.

Morey et al U.S. Pat. No. 4,067,502 and Morey U.S. Pat. No. 4,070,273show flotation separation of glass fragments (up to 10 mesh) usingamines as beneficiation agents.

Baxter U.S. Pat. No. 5,803,960 shows making glass for concretereinforcement, while avoiding the alkali-silica reaction (ASR) by mixinga lithium-containing composition with crushed bottle glass. The glassmay be provided in powder or fibrous form. Baxter et al U.S. Pat. No.5,810,921 shows a similar invention using chromium instead of lithium.

Pelot et al U.S. Pat. Nos. 6,344,081 and 6,699,321 show concretecompositions, and emphasize the use of “electric” or “E-glass” powder ofbetween 100 and 325 mesh in concrete. The claims require the glassparticles to be no larger than 80-120 mesh, 40-60% between 180 and 220mesh, and 10-30% less than 325 mesh; the cement used is to below-alkali. The glass is to comprise up to 25% of the mix.

Bergart U.S. Pat. Nos. 5,950,936 and 6,168,102 show a system forrecycling glass from a post-consumer waste glass stream including othersorts of debris. The process steps include various sorting, screening,crushing, presoaking, washing, dewatering, and drying steps. If a glasspowder is desired, second crushing and separation steps may be included.The dewatering step can be performed using a rotary screw conveyor (col.4, line 32 of the '936 patent), and the drying step using a fluidizedbed dryer (col. 4, line 44). It is acknowledged that some ceramiccontent will remain, and it is asserted that if the ceramic content isnot acceptable to the end user, a second crushing stage can be performedto form a fine glass powder; the “ceramic particles dispersed throughoutthe glass powder will dissipate in further processing”. Col. 5, lines48-52.

Kimmel et al U.S. Pat. No. 6,112,903 shows a method for sorting varioustypes of glass from one another. A stream of glass cullet mixed withother items is heated using microwave energy; as different types ofglass and items of other materials absorb different amounts of energy,they are differentially heated, and can be differentiated in a digitalimage made by a thermal imaging camera. A downstream diverter mechanismcan then be used to separate out various constituents of the stream.Kimmel et al U.S. Pat. No. 6,464,082 shows a complete system employingthis technique.

Harada U.S. Pat. Nos. 6,250,576 and 6,446,884 show a method and systemfor producing glass sands by crushing and agitating steps.

Sunde U.S. Pat. No. 6,743,287 shows a concrete using relatively largeglass particles, requiring addition of a “non-alkali reactive mineral”,e.g. granite.

Whaley U.S. Pat. No. 6,770,328 shows a method of making a terrazzosurface using recycled glass in an epoxy matrix. Preparation of theglass is not discussed.

Thus, although the prior art discusses the use of waste glass powder invarious applications, in particular as a partial substitute for cementin concrete, notes that post-consumer waste glass is not beingefficiently utilized, and provides some suggestions for processes forrecycling post-consumer waste glass, the art does not disclose areliable and efficient process for the production of suitably cleanedand dried glass powder from post-consumer waste glass and theintegration of that process into a process for the manufacture ofconcrete and concrete products, in particular one which does not requirethe addition of substances intended to suppress the alkali-silicareaction.

SUMMARY OF THE INVENTION

A method and apparatus are provided for processing post-consumer wasteglass, which can be expected to have residual substances adhering to itand which is likely also to be contaminated with foreign material, intoa clean dry fine powder that is ready for many applications. In accordwith one aspect of the invention, the method and apparatus permitproduction of a bright white glass powder using post-consumerwaste-glass.

A method is also provided for making concrete in which the glass powderreclaimed from post-consumer waste glass according to the invention isused as a partial substitute for Portland cement. The bright white glasspowder is a suitable partial substitute for white Portland cement inconcrete used to manufacture both white and colored concrete productsincluding architectural block, architectural concrete, cast stone,pavers, mortars and other cementitious products.

The method and apparatus provide for an integrated process for producingconcrete and concrete products employing powdered glass producedefficiently from post-consumer waste glass, and wherein no additives arerequired to suppress the alkali-silica reaction.

The method produces clean glass powder, and in accord with a preferredembodiment, white glass powder, from unsorted dirty post-consumer wasteglass by, broadly speaking, 1) employing glass pulverizing equipment toreduce waste glass to small fragments, allowing removal of trash, 2)employing a multistep washing process to clean the glass fragments, inthe preferred embodiment using aggregate cleaning equipment, 3) dryingthe fragments, preferably using fluidized bed techniques, and 4)grinding the glass to a desired particle size, preferably using a ballmill, in conjunction with an air classification step to produce a glasspowder of uniform particle size. For production of a white glass powder,the material compositions of the components used during the grindingprocess, e.g., drum of the mill and grinding media, are controlled.

The glass powder thus produced can be used as a partial substitute forPortland cement and even white Portland cement, in concrete andcementitious products, as a filler in paints and other products, and forother known uses for glass powder produced conventionally.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic depiction of the process of the invention forproducing glass powder from post-consumer waste glass;

FIG. 2 shows an elevational view of the equipment employed to perform afirst step in the process of the invention;

FIG. 3 shows a perspective, partly cut away view of a ball mill; and

FIG. 4 shows a cross-sectional view through a classifier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that the description is notintended to limit the invention to those embodiments. On the contrary,the invention is intended to cover alternatives, modifications, andequivalents, which may be included within the sprit and scope of theinvention as defined by the appended claims.

As noted above, the present invention relates to a new and improvedprocess for producing glass powder suitable for a wide range of usesfrom post-consumer waste glass and other waste glass as may beavailable, to the powder produced thereby, to the equipment forpracticing the process, and to the end uses of the powder thus produced.Accordingly, the invention allows a portion of the least recyclablewaste glass stream, that of mixed-color broken post-consumer wasteglass, now being disposed of primarily in landfills, to be turned to usein various products.

More specifically, a typical stream of post-consumer waste glass, asordinarily available from a municipal recycling facility, contains up to30% by weight of various trash, including metal items, paper, andplastic, as well as various organics, such as foodstuffs and residues,as well as a certain amount of dirt picked up in handling the wastestream. According to the invention the glass is separated from suchstreams and processed to a clean, dry, uniform glass powder suitable fora variety of applications, and specifically as a substitute for up toabout 40% of the Portland cement in concrete.

FIG. 1 shows the principal steps A-D in the process of the invention,and depicts equipment for the practice of each step schematically. Theadditional drawings which follow illustrate some of the equipmentcomponents in more detail, to fully enable the practice of theinvention.

The process begins with a first step A, termed Glass Reduction andDebris Removal. A stream 10 of post-consumer waste glass, including asubstantial fraction of non-glass trash as described above, as well asglass from other sources if available, is provided to a surge hopper 12.As is well known in the art, a surge hopper is essentially a bin,typically funnel-shaped, fitted with a metering device 14, such as areciprocating plate feeder, gate valve, or vibratory feeder, forcontrollably dispensing a solid material by gravity. In this case thesurge hopper is used to meter out the stream of waste glass, mixed togreater or lesser degree (typically up to 30% by weight, as mentioned)with various undesired items of metal, plastic, paper, ceramics,foodstuffs, and the like, onto a conveyor belt 16. Belt 16 feeds thestream into a pulverizer 18, which may be essentially as shown in U.S.Pat. No. 5,944,268 to James Andela.

The glass in the waste stream is selectively reduced by the pulverizerinto small fragments, typically ⅜″ or less maximum dimension, so thatthese glass fragments can effectively be removed from larger items ofnon-frangible materials, such as steel, aluminum, paper, and plastic, bysimple size-based separation. Paper, e.g., bottle labels, is usuallyremoved from the glass fragments in the pulverizer as well. The smallamount of ceramic material found in the typical stream of post-consumerwaste glass can be processed together with the glass without detriment.

The pulverized glass is then delivered by a further conveyor belt 20 toa trommel 22, for further separation of the glass fragments by size, andfurther removal of larger particles of unwanted material. For example,glass “sand” of ⅛″ or less is preferred for downstream processing, soglass fragments of larger size can be separated out and returned to thepulverizer, for further reduction, or can be set aside for use indifferent markets, e.g. as a constituent in asphalt for road-building.Trommel 22 may be as disclosed in U.S. Pat. No. 5,620,101 to Andela etal. Thus, in the first step A of the method, a stream ofcontaminate-free glass “sand” on the order of ⅛″ is produced using apulverizing and separation system comprising a surge hopper, pulverizer,and trommel. This process removes the larger fragments of extraneousmaterial such as metals and plastics that are included in the collectedglass, and pulverizes the glass into granules of substantially uniformsize.

Step B of the process involves washing the glass sand, as noted. Afterpulverizing, the glass granules are fed via a conveyor to a washingsystem that consists of an infeed hopper 24, two or more basins 26 and28 filled with water that is recirculated (that is, periodicallywithdrawn, filtered and returned), and a like number of helicalconveyors 30 and 32 encased in metal tubes. Thus, the glass granulesfall through the infeed hopper 24 into the first basin 26 where waterwashes the glass. In the basin, any paper and plastic that may remaintend to float to the surface, and can be removed, while sugars and otherorganic materials adhering to the glass particles are dissolved in thewater, while the glass particles sink. An auger screw 64 then picks upthe glass granules on the bottom of the basin and conveys them through ametal encased screen tube; at its end, the glass granules drop into asecond basin 28 and are washed again. A second encased auger screw 70then conveys the glass out of the system. The particles are dewatered toan extent as they are lifted by the screw conveyor; a further dewateringstep 71 can be incorporated before the subsequent drying step ifdesired. It will be appreciated that other forms of washing equipment,e.g., known wet screening or spray tumbling equipment, might instead beused.

Step C, as indicated, is that of drying the washed glass particles. Inthe preferred embodiment, this is accomplished by employment of afluidized bed drying system 34; however, it will be appreciated thatother forms of drying equipment, e.g., known tumbler drying equipment,or a rotary kiln, might instead be used. The design of suitablefluidized bed equipment is discussed in detail by Adham, ClassifyParticles Using Fluidized Beds, CEP Magazine, 54-57 (2001). Thefluidized bed apparatus 34 uses a furnace to dry the glass granules byforcing a stream of hot, pressurized air through the glass granules 38,shown resting on or suspended in the air stream just above a vibratingor oscillating perforated plate or screen 40. The process causes somelight weight materials such as glass fines to become airborne. Tocapture these fines and to trap the hot air for recirculation, the bedhas a dust collector 42 over its top. The vibrating screen 40 thentransports the glass granules to the exit of the fluidized bed equipment34, from which they are transported to step D.

Step D involves grinding the glass particles, as noted above typicallyof ⅛″ or less, to a fine powder of 325 mesh minus. The preferredequipment for this step is a ball mill 44. Ball milling is a well-knownprocess capable of rapidly grinding the glass particles to colloidalfineness. Briefly, ball milling is accomplished by admitting a quantityof the glass sand to a rotating steel drum, together with grindingmedia, such as high mass balls. The balls may be, e.g., steel balls.However, where metal is used for the drum inner surface and grindingmedia, there is the potential for metal microparticulates to discolorthe powder and result in the powder acquiring a grayish tint If thedesired end result is a bright white glass powder, the millingprocessing is modified to increase the brightness of the powder. Morespecifically, the drum of the ball mill 44 is lined with a non-metal,such as stone, and preferably jasper quartz. The jasper quartz ispreferably five to six inches thick and adhered to the inner surface ofthe drum by way of rapid-set high-strength cement. In addition, thegrinding media has a non-metallic surface. The grinding media ispreferably ceramic cylinders that are preferably 1 to 1¼ inches indiameter and preferably 1 to 2 inches in length. Ceramic media of othershapes and sizes, including spherical and conical can also be used. Allsuch shapes of ceramic grinding media are considered ceramic ball mediafor the grinding mill process. The ceramic media and glass arepreferably provided in the drum in a volumetric ratio of 3:7 to 7:3. Theceramic ball media is advantageous to a continuous process; when theball media grinds down from use over time, new ball media is addedwithout disrupting the continuous process. As a less desirablealternative, ceramic-coated or other non-metallic coated grinding mediacan be used. However, as the coating is worn away from the grindingmedia during the grinding process, the continuous process may need to betemporarily halted to replace some or all of the grinding media.

It will be appreciated that other forms of fine grinding equipment,e.g., vibratory rod mills or jet mills, might be used instead.

The glass powder produced by the mill is then conveyed via a pneumaticconveyor to a classification system 46 which captures the 325 mesh orsmaller powder by using vacuums to pull this material away from anyheavier material. The heavier material is then sent back to the ballmill as indicated at 48 for further grinding, or can be collected forother uses if desired. Having thus been reduced to a 325 mesh or smallersize, the glass is ready for use in various applications, e.g., asindicated at 52 as a partial replacement for Portland cement as aconstituent in concrete blocks.

As mentioned above, FIG. 2 shows an elevational view of the equipmentemployed to perform the first step A in the process of the invention,that is, reduction of irregularly-sized glass objects and fragments, astypically found in post-consumer waste streams, to substantiallyuniformly sized glass particles, while removing trash therefrom,including paper, metal, and plastic. As described above, a typicalstream of post-consumer waste glass, as obtained from the typicalmunicipal waste facility, may in fact contain up to 30% by weight ofnon-glass trash of various sorts, which must be removed from the glassin the stream.

The stream of post-consumer glass and admixed undesirable material 10 isadmitted to the surge hopper 12. A suitable surge hopper 12 is availablefrom Andela Products, Ltd. of Richfield Springs, N.Y. under model numberAMSH-86F. A reciprocating plate feeder 14 controls flow of the streamonto a first conveyor 16, which transports it to pulverizer 18. Amagnetic separator is preferably mounted above conveyor 16, to removeferrous material from the process stream. A suitable pulverizer isavailable from Andela Products, Ltd. of Richfield Springs, N.Y. undermodel number GP-2. As noted, pulverizer 18 may be as disclosed in U.S.Pat. No. 5,944,268 to Andela, incorporated herein by this reference. Asdiscussed therein, pulverizers so designed efficiently reduce frangiblematerials such as glass to small fragments, typically ⅛″ in maximumdimension, while allowing much larger items of nonfrangible materials,such as paper, plastic, aluminum and steel, to pass through, enabling asimple size-based separation to be carried out.

More specifically, selective reduction of glass takes place inside thepulverizer due to the design of the preferred flexible impactors orflails as disclosed in Andela U.S. Pat. No. 5,944,268 mentioned above.As discussed therein, the pulverizer preferably comprises a pair ofshafts each carrying a number of flexible flails rotating centrallywithin relatively closely-fitting cylindrical housings. A “tornado” typeof air flow pattern created by the flails breaks the glass (or otherbreakable material) into fine granules, the edges of which are roundedas these particles collide with each other. However, items of materialsthat do not break well on impact, such as paper, plastics and metal,remain relatively whole in the tornado and exit the pulverizer as largeritems, allowing a simple size based process to be used to separate thesmall glass granules from the larger fragments of undesired materials.The flexibility of the flails allows them to deflect, allowing plasticcontainers and cans to slide past the flails, so that such items are notshredded and the flails are not damaged. There are no internal screensor pinch points in the pulverizer that causes material to be reducedthrough any kind of “grinding” action; the glass particles are reducedby mutual contact. Paper such as bottle labels is effectively removed inthe pulverizer as well; any remaining paper adhering to the glassparticles is removed in the subsequent washing step.

A second conveyor 20 then carries the glass particles to the trommel 22.A suitable trommel is available from Andela Products, Ltd. of RichfieldSprings, N.Y. under model number ATROM-104. As discussed, this equipmentmay be essentially as described in U.S. Pat. No. 5,620,101 to Andela. etal, incorporated herein by this reference. As shown in detail therein,the trommel comprises a cylinder comprising two coaxial screens ofdiffering mesh sizes, which are rotated about an axis inclined at aslight angle to the horizontal. Accordingly, a size-based separationtakes places as the mesh drum rotates and the particulate material movestherealong, with the smaller particles falling through the finer mesh atthe upper end of the mesh drum, and so on. The effect is to sort thesmallest glass particles into a first bin 54, labeled “sand” in FIG. 2;particles of up to a larger size fall into a second bin 56, labeled“gravel”; the remainder, typically larger particles or items ofmaterials other than glass, is conveyed by a third conveyor 58 into athird bin 60 labeled “trash”. Preferably, the larger-size glassparticles collected in the “gravel” bin 56 are returned to thepulverizer 18, to be further reduced, so that ultimately the highestpossible fraction of the post-consumer waste glass stream is reduced toa small “sand” particle size, preferably ⅛″ or less.

Step B in the process of the invention is that of washing theparticulate glass. As discussed above, this can be accomplished usingscrew or auger washing equipment. Equipment generally suitable for thisstep is sold under the trade name “Scrommel” by a company of that name,located in Salinas, Kans., for separating out the constituents ofuncured concrete for reuse, and is illustrated schematically at step Bin FIG. 1.

As discussed above, this equipment may comprise a first settling basin26 into which the particulate material is dropped; a second surge hopper24 may be provided to regulate the flow. Basin 26 is filled at leastpartially with water, as indicated at 62. If necessary, detergent or thelike may be added to ensure the cleanliness of the glass. As mentionedabove, any paper and plastic remaining in the stream of glassparticulates tends to float to the surface of the water in the basin,and can be readily removed, while sugars and other organic materialsadhering to the glass particles are dissolved in the water, and theglass particles sink.

A first helical screw conveyor 30, comprising an auger 64 driven forrotation by a motor 68, with its lower end extending into the settlingbasin 26, and fitting relatively tightly into a tubular enclosure 66,draws the particulate glass from the bottom of the basin 26 alongenclosure 66. The glass then drops into a second settling basin 28associated with a second similar helical screw conveyor 32, from whichit is removed by a second similar auger 70. For further size separation,the first screw conveyor 30 can be fitted with a screen fitting aroundthe auger screw, allowing smaller material to fall through the screen,and out an exit aperture in the enclosure; in this case the smallermaterial would be conveyed to the next stage in the process, and thelarger material returned for further reduction or separation.

The washing stations thus provided can of course be multiplied ifnecessary, and detergents, solvents, or heated water can be employed.Dewatering takes place as the particulate glass travels upwardly alongthe screw conveyors; further dewatering can be performed, e.g., usingcentrifuge equipment, between this washing step and the subsequentdrying step, as indicated at 71.

FIG. 1 also shows schematically at C the next step in the process of theinvention, drying the washed glass. As illustrated, in the preferredembodiment the glass particles are dried using fluidized bed equipment,although other known drying equipment, such as rotary kiln equipment, isof course also within the scope of the invention. As mentioned above,the design of fluidized bed equipment, in particular for classificationof particles by size, is discussed in detail by Adham, ClassifyParticles Using Fluidized Beds, CEP Magazine, 54-57 (2001).

The basic operation of such equipment is as follows, referring toFIG. 1. The particulate product to be classified and/or dried isintroduced to the equipment 34 as at 72, e.g. by conveyor from thepreceding step. A perforated or slotted plate or screen 40 may beprovided to support the product as necessary, and is oscillated to movethe product along, as indicated by arrows 76. A high-velocity stream ofair, ordinarily heated, is introduced at 36. As indicated at 78, the airstream is ducted so as to blow upwardly through the “floor” provided byplate 40. The effect is to blow the incoming particulates into the airvolume above plate 40, suspending them in the air stream, and thusforming the so-called fluidized bed. Clearly the particles in the bedwill be buffeted by the heated air stream, and will be very effectivelydried. The heavier particulates can be removed at 82, as they fall offthe end of the oscillating plate 40. As the smaller particles or “fines”are lighter for their relative size, they will be lifted furtherupwardly by the air stream, and may be removed along with the exhaustedair at 80. The heated air can be separated from the fines, filtered toremove the likely dust and particles of paper and the like, as well assome pulverized glass, and returned to the inlet of the apparatus usedto heat the inlet air stream, saving some heating cost. A furthervibratory screen might be added directly after the dryer, e.g., toperform a further size-based separation to further classify the glassgranules for other markets.

As indicated above, the final principal step in the process of makingglass powder from a typical stream of post-consumer waste glassaccording to this aspect of the invention is grinding the particulateglass to a powder of uniform size, preferably 325 mesh or less. Asillustrated in FIG. 1, this can be accomplished using ball millingequipment 44 for the grinding step, with a classifier 46 provided toensure that any larger material that may avoid reduction is returned tothe ball mill for further grinding. FIG. 3 shows a perspective, partlycut away view of a ball mill 44 and FIG. 4 shows a cross-sectional viewthrough a particular type of classifier 46. Other types of grinding andclassification equipment are within the scope of the invention.

As discussed above, and as illustrated by FIG. 3, in one embodiment, theball mill 44 comprises a steel drum 86, typically round or polygonal incross-sectional configuration, supported for rotation about a centralaxis as indicated at 88. If the grinding is performed in a batchprocess, a quantity of glass particulates to be ground are charged intothe drum 86 through an inlet port (not shown), along with a number ofsteel balls or similar heavy objects. As the drum is rotated, the ballsgradually reduce the particulates to powder. After a suitable period oftime, the powder is removed, again through a port (not shown).Alternatively, ball mills are known with continuous inlet and outletflow, and these are also within the scope of the invention.

In accord with another embodiment, the drum of the ball mill 44 is stonelined, and more preferably jasper lined. In addition, the balls of theball mill have a non-metallic surface, and are preferably of a ceramiccomposition. This construction prevents the powder from acquiring metalmicroparticulates which can discolor the powder. The resulting glasspowder is bright white in color.

After milling, the powder is then preferably conveyed, typically by anair stream, to the inlet of a classifier 46. Suitable equipment, asillustrated in FIG. 4, is available from Comex AS, Trondheim, Norway.Where the desired product is a bright white glass powder the relevantsurfaces of the classifier are optionally coated in a ceramic materialto prevent any discoloration to the powder. The stream of glass powderand remaining larger particles in air enters the classifier 46 through avertical inlet 90 at the lower extremity of the unit. A motor 92 drivesa rotor 94, pulling the inlet stream upwardly. The stream is dispersedaround a static distribution cone 96, where coarse particles immediatelysettle in the lower velocity air stream, and are urged toward theconical outlet and fall toward the bottom of the classifier, to bewithdrawn at 100. Secondary air is introduced at a further tangentialinlet 98, to wash off finer particles that might otherwise adhere to thecoarse particles. Fines introduced with the inlet stream are pulledthrough the rotor and exit at 102; these form the powdered glassproduced according to the process of the invention, and accordingly areconveyed to an end use, bagged for storage or shipment, or simplyaccumulated in a bin. As mentioned above, and depending on the values of“coarse” and “fine” in the actual operation of the classifier 46, thecoarse particles may be returned to the ball mill 44 for furtherreduction.

An advantage of a continuous process according to the invention is thatsignificantly increased consistency is provided to the powdered glass.The particles drawn out through the exit 102 of the classifier fallunder a predictable and narrow distribution curve of quantity to size.The increased consistency provides greater performance when used as acementitious product. In batch process milling, the particle size of theglass powder has a wider distribution curve, which may result in (i) aninitially faster and higher temperature cementitious reaction (which maybe less desirable) and (ii) as a result of relatively larger particlesize, some of the glass powder may remain unreactive in the cementitiouspaste. Therefore, a continuous process provides more uniform andconsistent results which provides superior strength for the end resultconcrete product. Thus, glass powder produced according to the method ofthe invention when used as a partial replacement for Portland cement asa binder in concrete is a superior product. Following are examples ofprocesses for making concrete blocks and ready-mix concrete.

Concrete as used in masonry products, e.g., block, consists of acombination of various components. These include Portland cement whichacts as a cementitious binder; fine and coarse aggregates; chemicaladmixtures; and various pozzolans that supplement cement. These includebut are not limited to ground blast furnace slag and fly ash. Thesematerials are combined with water and mixed to a uniform consistency tocreate concrete.

According to one aspect of the invention, powdered glass made accordingto the process described in detail above may be used as a replacementfor up to 40% of the Portland cement content of otherwise conventionalconcrete. As is conventional for pozzolanic materials, at least 60% ofthe glass powder thus produced should be 325 mesh size or finer, andshould contain no more than 2% moisture. More specifically, when using afine glass powder as above as a substitute for Portland cement accordingto the invention, no additives need to be added to suppress thealkali-silica reaction (“ASR”) that occurs when larger fragments ofglass of certain compositions is employed as a component of concrete.

Manufacture of concrete using the glass powder according to theinvention in partial substitution for Portland cement involves generallyconventional processing steps. The component materials are to be mixedin a mixer for a minimum of 3 minutes. Under simultaneous vibration andcompaction in steel molds, the mixture can be formed into various shapesand sizes for the masonry market. The formed products are placed oncuring racks for a pre-set time, typically a minimum of 2 hours. Oncepre-set, the products are placed in a curing chamber in which theambient air is saturated with steam to further cure the concrete of theproducts. Within 24 hours the various masonry products may be packagedand prepared for shipment.

In making ready-mix concrete, various components, primarily comprisingPortland cement as a cementitious binder and aggregates, are combinedwith a pre-measured amount of water to form concrete. Again, as above,according to one aspect of the invention, powdered glass made accordingto the process described in detail above may be used as a replacementfor up to 40% of the Portland cement content of otherwise conventionalconcrete. The powdered glass is to be charged into a mixer at the sametime the Portland cement is added to the remaining components. Afterthorough mixing, typically for a minimum of 5 minutes, the concretecontaining glass powder produced according to the invention may beplaced in the same manner as conventional concrete.

Similarly, glass powder produced according to the invention can be usedin other known application for powdered glass, for example in paints andas fillers.

It should be appreciated that the pozzolanic white glass powderdescribed herein has significantly higher value than other pozzolanicglass powder produced from post-consumer waste glass. White glass powdercan be used as a replacement for costly white Portland cement, e.g., inthe manufacture of white and colored architectural block. Slag, fly ash,and gray Portland cement are unsuitable replacements for white Portlandcement in such specialized applications, as their non-white coloringswill prevent achievement of certain vivid colorations, including white,in the end product. White Portland cement can cost more than twice thatof grey Portland cement. White glass powder provides a suitable partialreplacement for white Portland cement from the post-consumer wastestream. A white glass pozzolan made from mixed colored glass has abrightness value of 77 to 80 (using the ASTM E 313 standard practice).White Portland cement has brightness values in the range from 75 to 85;slag has a brightness generally in the range of 60 to 65, while thebrightness of fly ash is even lower.

Concrete products which include pozzolanic glass powder manufacturedfrom post-consumer waste glass as a partial substitute for Portlandcement are substantially more environmentally beneficial than otherconcrete products. Post-consumer waste glass is generally the mostdifficult type of waste glass to recycle into a different product, asthe waste stream is dirty, of various quality and type, unsorted, andadmixed with trash that must be separated during the process. Moreover,such aspects of post-consumer waste glass presents hurdles for achievinga method of continuous processing of a post-consumer waste glass streamthat are required to be overcome in order to provide an economy of scalenecessary for commercial production of a glass powder pozzolan from suchsource and a consistency of product necessary for proper cementitiousreaction. However, once properly achieved, the resulting products havean environmentally beneficially impact significantly greater thanconcrete products made from other waste glass streams.

In fact, recycling of the post-consumer waste glass stream into a glasspowder pozzolan is not just beneficial to the environment, but carriesover into direct financial benefits to the end user of concrete productsmanufactured therewith. For example, buildings manufactured with suchconcrete products can be marketed as ‘green’ buildings, which can be asignificant marketing aspect for architects to spec such concreteproducts into a construction product, for developers to request suchbuilding products, and for tenants finding buildings attractive becausecertain buildings have been manufactured from such building materials.Using post-consumer waste glass as a pozzolan in the concrete productsfor construction purposes provides significant advantages.

For example, the LEED (Leadership in Energy and Environmental Design)green building rating system developed by the U.S. Green BuildingCouncil provides LEED certification for new construction and renovationprojects. LEED is a point based system in which projects earn points forsatisfying specific green building criteria, including the use ofpost-consumer recyclable materials. The higher the total number ofpoints has been shown to translate into increased occupancy rates,higher chargeable rents, and additional tax credits for the builder.Therefore, it is appreciated that the use of post-consumer waste glassas a pozzolanic constituent of the concrete building materials hasadvantage not provided by the concrete building materials incorporatingpre-consumer post-industrial waste materials.

Accordingly, those of skill in the art will appreciate that according tothe invention readily available post-consumer waste glass is removedfrom the waste stream and processed to create glass powder in industrialquantities that can be used in many applications. More specifically,according to the invention, part of the post-consumer waste glass streamthat is normally directed into landfills is diverted and processed intoa powder that is clean and dry enough for applications that are usuallyreserved for glass powder developed from new glass or industrial wasteglass only. Moreover, this is accomplished using machinery from multipleindustries employed in a unique, novel, and unobvious way to pulverize,wash, dry, and classify the post-consumer waste glass into a white glasspowder. However, although the invention is described herein asimplemented using particular machinery, this in no way should limit thescope of the invention but as merely providing illustrations of some ofthe presently preferred embodiments of this invention.

1.-21. (canceled)
 22. A white glass powder manufactured by a process,comprising: a) supplying a stream of mixed-color post-consumer wasteglass containing organic contaminants and items of non-frangiblematerials; b) then pulverizing the stream in a manner such that consumerwaste glass in the stream is reduced to fragments of average maximumsize ⅛ inch or less, while non-frangible items are not reduced to saidsize; c) then performing a size-based separation of the reduced glassfragments from the non-frangible items; d) then washing the reducedglass fragments to separate plastic and paper fragments and organiccontaminants therefrom; e) then drying the washed glass fragments to amoisture content of no more than about 2% by weight; f) then grindingthe dried glass fragments into a white powder having a brightness of atleast 77 using the ASTM E 313 standard practice, wherein the grinding isperformed in a mill that grinds media having a non-metallic surfaceagainst the dried glass fragments; g) then removing the white glasspowder; h) then returning the remaining particles to said grinding stepfor grinding with additional dried glass fragments received for grindingfrom after said drying step; and i) repeating steps g) and h) forcontinuous manufacturer of the white glass powder.
 23. A white glasspowder according to claim 22, wherein: said white powder has abrightness of 77 to 80 the ASTM E 313 standard practice.
 24. A whiteglass powder according to claim 22, wherein: the mill of said grindingstep includes a drum lined with a non-metallic surface that does notimpart a non-white discoloration to the powder during grinding.
 26. Awhite glass powder according to claim 25, wherein: said drum is linedwith stone.
 27. A white glass powder according to claim 24, wherein:said grinding media are balls having a ceramic surface.
 28. A whiteglass powder according to claim 27, wherein: said grinding media aresolid ceramic.
 29. A white glass powder according to claim 22, wherein:a classifier coated with a non-metallic material is used for saidremoving and said returning.
 30. A white glass powder according to claim22, wherein: at least 60 percent of said white powder has a size of 325mesh or smaller.
 31. A white glass powder manufactured from a stream ofpost-consumer mixed color waste glass containing items of non-frangiblematerials, said white glass powder made from the process of: a)pulverizing the stream in a manner such that consumer waste glass in thestream is reduced to fragments of an average maximum size, whilenon-frangible items are not reduced to said size; b) then performing asize-based separation of the reduced glass fragments from thenon-frangible items; c) then washing the reduced glass fragments; d)then drying the washed glass fragments; and e) then grinding the driedglass fragments into a powder in a mill, said mill having a non-metallicsurface lining a grinding chamber of said mill such that the dried glassfragments and the white powder are in contact with said non-metallicsurface of said mill while said mill is grinding the dried glass,wherein said non-metallic surface does not impart a non-whitediscoloration to the powder during grinding such that the resultingpowder has a brightness of at least 77 using the ASTM E 313 standardpractice.
 32. A white glass powder according to claim 31, wherein: saidwhite powder has a brightness of 77 to 80 the ASTM E 313 standardpractice.
 33. A white glass powder according to claim 31, wherein: saidnon-metallic surface is stone.
 34. A white glass powder according toclaim 33, wherein: said stone is quartz.
 35. A white glass powderaccording to claim 31, wherein: said grinding includes grinding in saidgrinding chamber with grinding media, said grinding media having anon-metallic surface.
 36. A white glass powder according to claim 35,wherein: said grinding media has a ceramic surface.
 37. A white glasspowder according to claim 36, wherein: said grinding media are ceramiccylinders.
 38. A white glass powder according to claim 31, furthercomprising: classifying said white glass powder with a classifier thatseparates the white glass powder from remaining larger glassparticulate, said classifier lined with a non-metallic material along apathway through which said glass powder is moved during the separation.39. A white glass powder according to claim 38, wherein: said classifieris an air classifier.
 40. A white glass powder manufactured from astream of post-consumer mixed-color waste glass containing organiccontaminants and items of non-frangible materials, said white glasspowder being free of organic contaminants and non-frangible materials,at least 60 percent of said white glass powder having a particle sizenot exceeding 325 mesh, and said white glass powder having a brightnessof at least 77 using the ASTM E 313 standard practice.
 41. A white glasspowder according to claim 40, wherein: said white powder has abrightness of 77 to 80 the ASTM E 313 standard practice.